I. Pathogenesis is due to degenerative changes and herniation of the lumbar disc, which stimulates the nerve roots and sinus nerve to produce a series of clinical manifestations. (1) Degenerative changes of the lumbar disc: degeneration of the nucleus pulposus is mainly manifested as a decrease in water content, and can cause small-scale pathological changes such as destabilization and loosening of the pushed joints due to water loss; degeneration of the fibrous ring is mainly manifested as a decrease in the degree of toughness. (2) The effect of external force: the slight damage caused by long-term repeated external force acts on the lumbar intervertebral disc over time and aggravates the degree of degeneration. (3) Weakness of the disc’s own anatomical factors: (1) The disc gradually lacks blood circulation and has poor repair ability after adulthood. On the basis of the above factors, some triggering factors that can lead to a sudden increase in pressure on the intervertebral disc may cause the less elastic nucleus pulposus to pass through the less tough fibrous ring, thus causing the nucleus pulposus to protrude. The pathogenesis 1, the main cause is known, the lumbar intervertebral disc in the spine load and movement under strong compressive stress. After about 20 years of age, the disc begins to degenerate and constitutes the basic etiology of lumbar disc herniation. In addition, lumbar disc herniation is associated with the following factors: (1) Trauma: Observations of clinical cases show that trauma is an important factor in disc herniation, especially in children and adolescents, and is closely related to its onset. During mild spinal loading and rapid rotation, horizontal rupture of the annulus fibrosus can be caused, while compressive stresses mainly rupture the cartilage endplates. It is also believed that trauma is only a causative factor for disc herniation, and that the original lesion lies in the painless nucleus pulposus protruding into the inner fibrous ring, while trauma causes the nucleus pulposus to protrude further into the outer fibrous ring, which is innervated by nerves, thus causing pain. (2) occupation: occupation and lumbar disc protrusion (prolapse) is very close, for example, car and tractor drivers in a long-term sitting and bumpy state, so that when driving a car, the pressure in the intervertebral disc is high, up to 0.5kPa/cm2, and the pressure can increase to 1kPa/cm2 when the clutch is stepped on, easily causing lumbar disc protrusion. Those who engage in heavy physical labor and weightlifting are more likely to cause disc degeneration due to excessive load, as the pressure in the disc can increase to more than 30kPa/cm2 if a 20kg weight is lifted in a bent over state. (3) Genetic factors: there are reports of familial onset of lumbar disc herniation, but there is less material in China; in addition, statistics show that the incidence of Indians, African blacks and Inuit is significantly lower than the incidence of other ethnic groups, and the reasons for this need further study. (4) Lumbosacral congenital anomalies: deformities of the lumbosacral segment can increase the incidence, including lumbosacralization, sacral lumbarization, hemivertebral deformity, small joint deformity and asymmetry of the articular eminence. The above-mentioned factors can make the stress on the lower lumbar spine change, thus constituting one of the factors that increase the internal pressure of the intervertebral disc and predispose to degeneration and injury. 2, triggering factors In addition to the above-mentioned main causes, that is, degenerative changes in the intervertebral disc, various triggering factors also play an important role, for example, some factors that slightly increase the abdominal pressure can make the nucleus pulposus protrude. This is mainly due to a sudden increase in intervertebral disc pressure based on degenerative disc degeneration, which causes the free nucleus pulposus to cross the degenerated and thinned annulus fibrosus into the front of the spinal canal or through the vertebral plate into the vertebral body edge. (1) Increased abdominal pressure: About 1/3 of clinical cases have clear factors that increase abdominal pressure before the onset, such as violent coughing, sneezing, breath-holding, forceful defecation, or even “false respect” movements, which can raise the abdominal pressure and disrupt the equilibrium between the vertebral segment and the spinal canal. (2) lumbar posture: whether during sleep or in daily life, work, when the lumbar in a flexed position, such as a sudden rotation, it is easy to induce a herniated nucleus pulposus. In fact, in this position, the pressure in the intervertebral space is also higher, which can easily induce the nucleus pulposus to protrude to the rear. (3) Sudden weight-bearing: A well-trained person does more preparatory activities first, or starts to carry weight from small weights (such as lifting weights, carrying a load, etc.) to prevent lumbar sprain or disc protrusion, but if the lumbar load suddenly increases, it may not only cause lumbar sprain, but also easily cause nucleus pulposus protrusion. (4) Pregnancy: the entire ligament system is in a relaxed state during pregnancy, the posterior longitudinal ligament relaxation is easy to make the disc bulge. In this regard, the authors conducted a study and found that at this time, the incidence of low back pain in pregnant women is significantly higher than in normal people. In conclusion, the triggering factors that cause lumbar disc herniation are more complex, although various experiments have been conducted, but due to the inferred nature of animal experiments, the distortion of fresh cadaver specimens, and the limitations of biomechanical testing of the peri-spinal tissues, etc., the exact factors that trigger the disease and its mechanism have not yet been truly identified, and further study is needed. (5) Protrusion of degenerated nucleus pulposus by trauma to the lumbar region. (6) Cold and moisture. Cold or humidity can cause small blood vessel constriction and muscle spasm, which increases the pressure on the disc and may also cause the degenerated disc to crack. Extrinsic factors are excessive weight bearing or rapid bending, lateral flexion, rotation to form a rupture of the fibrous ring, or lumbar trauma, improper posture in daily life and work, can also occur lumbar disc herniation. 3, lumbar disc herniation prevalent population: (1) from the age: lumbar disc herniation prevalent in young adults. (2) from the gender: lumbar disc herniation is mostly seen in men, the incidence of men is higher than women, it is generally believed that the ratio of men to women is 4 to 12:1. (3) from the body type: generally too obese or too thin people are prone to lumbar disc herniation. (4) Occupationally speaking: industrial workers with high labor intensity are more common. However, the incidence rate of brain workers is not very low at present. (5) From the posture point of view: poor work posture. The incidence is more common in workers who work in a row, salesmen who often stand, and textile workers. (6) In terms of living and working environment: often in cold or humid environment, all to a certain extent become the conditions that induce lumbar disc herniation. (7) In terms of different periods of women: prenatal, postnatal and menopause are the risk periods for lumbar disc herniation in women. (8) People with congenital lumbar spine dysplasia or deformity, or even those who are too mentally stressed are prone to lumbar pain, and people who smoke may be related to the fact that coughing can cause an increase in the internal pressure of the intervertebral disc and the pressure in the spinal canal, making it easy for degenerative changes to occur. Clinical symptoms of lumbar disc herniation can vary greatly according to the location and size of the nucleus pulposus (protrusion) and the size of the sagittal diameter of the spinal canal, pathological characteristics, body state and individual sensitivity. Therefore, the recognition and determination of the symptoms of this disease must be fully understood and inferred from the perspective of its pathophysiology and pathological anatomy. The common symptoms of the disease are described as follows. (1) Low back pain: More than 95% of patients with lumbar disc protrusion (prolapse) have this symptom, including those with vertebral body type. (1) Mechanism: It is mainly due to mechanical irritation and compression of adjacent tissues (mainly nerve roots and sinus-vertebral nerves) caused by the degenerated nucleus pulposus entering the vertebral body or the posterior longitudinal ligament, or chemical and/or mechanical radiculitis caused by stimulation of adjacent spinal nerve roots or sinus-vertebral nerves due to the release of glycoprotein, β-protein and histamine (substance H) in the nucleus pulposus. ② Manifestation: clinically, persistent dull pain in the low back is common, which is relieved by lying down and aggravated by standing, and can be tolerated under normal circumstances and allows moderate lumbar activities and slow walking, mainly due to mechanical compression. The duration is as little as 2 weeks and as long as several months or even years. The other type of pain is severe lumbar spasm-like pain, which not only has a sudden onset, but also is unbearable and cannot be tolerated without bed rest. This is mainly due to ischemic radiculitis, that is, the sudden protrusion of the nucleus pulposus compressing the nerve root, resulting in a series of changes such as ischemia, bruising, hypoxia and edema due to the simultaneous compression of the root blood vessels, and can last for several days to weeks (while this sign can also occur in spinal stenosis, but the duration is very short, only a few minutes). The effect of early relief can be achieved by lying on a plank bed, closed therapy and various dehydrating agents. (2) Lower extremity radiating pain: more than 80% of cases have this symptom, with posterior type up to 95% or more. (1) Mechanism: The same mechanism as the former, mainly due to mechanical and/or chemical stimulation of the spinal nerve roots. In addition, reflex sciatica (or “pseudosciatica”) may also occur through the sinus nerve of the affected node. ② Manifestation: In mild cases, it is a radiating tingling or numbness from the lumbar region to the back of the thigh and calf, reaching the bottom of the foot; it is usually tolerable. In severe cases, it is a severe electric shock-like pain from the waist to the foot, and is mostly accompanied by numbness. In mild cases, although the pain is still walkable, the gait is unstable and lame; the waist is tilted forward or the waist is held by hand to relieve the tension on the sciatic nerve. In severe cases, the patient rests in bed and prefers to adopt the hip flexion, knee flexion and lateral position. All factors that increase abdominal pressure aggravate radiating pain. Since flexion of the neck can aggravate the stimulation of the spinal nerve by pulling on the dural sac (i.e., flexion test), the patient’s head and neck are mostly in the supine and extended position. The radiological pain is mostly one-sided in the limbs, and only a very small number of central or paracentral herniated nucleus pulposus patients show symptoms in both lower limbs. (3) Numbness of the limbs: Most of them are accompanied by the former, and only about 5% of them show numbness without pain. This is mainly due to the stimulation of proprioceptive and tactile fibers in the spinal nerve roots. The extent and location depends on the number of nerve root sequences involved. (4) Cold sensation in the extremities: A small number of cases (about 5% to 10%) feel cold and chilly in the extremities, mainly due to the stimulation of sympathetic nerve fibers in the spinal canal. Clinically, it is common to find cases in which the patient complains of feverish limbs on the day after surgery, which is the same mechanism as this. (5) Intermittent claudication: The mechanism and clinical manifestations are similar to those of lumbar spinal stenosis, mainly due to the pathological and physiological basis of secondary lumbar spinal stenosis that can occur in the case of herniated nucleus pulposus; for those with congenital developmental sagittal narrowing of the spinal canal, the prolapsed nucleus pulposus aggravates the degree of stenosis of the spinal canal, making it easy to induce this symptom. (6) Muscle paralysis: paralysis caused by lumbar disc protrusion (prolapse) is very rare, but mostly due to root damage resulting in different degrees of paralysis of the innervated muscles. In mild cases, the muscle strength is reduced, and in severe cases, the muscle loses its function. Clinically, foot drop caused by the involvement of the anterior tibialis, long and short peroneal muscles, long and long toe extensors and M long extensors innervated by the lumbar 5 spinal nerve is the most common, followed by the quadriceps (innervated by the lumbar 3-4 spinal nerve) and gastrocnemius (innervated by the sacral 1 spinal nerve). (7) Cauda equina symptoms: mainly seen in the posterior central type and paracentral type of myelomeningocele (prolapse), so it is rare clinically. The main manifestations are numbness and tingling in the perineum, defecation and urination disorders, impotence (in men), and symptoms of sciatic nerve involvement in both lower extremities. In severe cases, symptoms such as loss of bowel control and incomplete paralysis of both lower limbs may occur. (8) Lower abdominal pain or anterolateral thigh pain: In high lumbar disc herniation, when the lumbar 2, 3, and 4 nerve roots are involved, there is pain in the groin area of the lower abdomen or anteromedial thigh in the area innervated by the nerve roots. In addition, some patients with low lumbar disc herniation may also present with pain in the inguinal region or anterior medial thigh. Those with lumbar 3 to 4 disc herniation have pain in the inguinal region or anterior medial thigh in 1/3 of them. The rate of occurrence in those with disc herniation between lumbar 4 to 5 and lumbar 5 to sacral 1 is almost equal. This pain is mostly referred pain. (9) Low skin temperature of the affected limb: similar to cold sensation of the limb, it also reflexively causes sympathetic vasoconstriction due to pain in the affected limb. This may be due to provocation of the sympathetic nerve fibers in the paravertebral area, causing sciatica and lowering of skin temperature in the lower legs and toes, especially in the toes. This hypothermia is more pronounced in those with sacral 1 nerve root compression than in those with lumbar 5 nerve root compression. On the contrary, after the removal of the nucleus pulposus, the feverish sensation of the limb will appear. (10) Others: Depending on the location and degree of compression of the compressed spinal nerve roots, the extent of involvement of adjacent tissues and other factors, certain rare symptoms such as excessive sweating of the limbs, swelling, sacrococcygeal pain and radiating pain of the knee may also appear. 2. Signs of lumbar disc herniation (1) General signs: mainly refers to lumbar and spinal signs, which are common to the disease, including: ① Gait: in the acute stage or when the nerve root is obviously compressed, the patient may have a limp, a hand on the waist or the affected foot is afraid of weight bearing and a jumping gait. In mild cases, the gait may be the same as that of a normal person. ②Lumbar spine curvature changes: general cases show the disappearance of the physiological curve of the lumbar spine, flat back or reduced forward convexity. In a few cases, there is even a posterior convexity deformity (mostly in combination with lumbar spinal stenosis). (iii) Scoliosis: this sign is generally present. Depending on the relationship between the site of the herniated nucleus pulposus and the nerve root, the spine may be curved to the healthy side or to the affected side. If the herniated nucleus pulposus is located on the medial side of the spinal nerve root, the lumbar spine bends to the affected side because the spine bends to the affected side to reduce the tension of the spinal nerve root; conversely, if the herniated nucleus pulposus is located on the lateral side of the spinal nerve root, the lumbar spine bends to the healthy side (Figure 1). In fact, this is only a general rule, but many factors, including the length of the spinal nerve, the degree of traumatic inflammatory response in the spinal canal, the distance of the protrusion from the spinal nerve root, and various other causes can change the direction of scoliosis. ④ Pressure pain and percussion pain: The site of pressure pain and percussion pain basically coincides with the vertebral segment of the lesion and is positive in about 80% to 90% of cases. The percussion pain is obvious at the spinous process and is caused by percussion vibration of the lesion. The pressure point is mainly located at the paravertebral area equivalent to the sacrospinous muscle. Some cases were accompanied by radiating pain in the lower extremities, which was mainly due to the stimulation of the dorsal branch of the spinal nerve root. In addition, percussion of the bilateral heels may also cause conductive pain. In combination with lumbar spinal stenosis, there is also significant pressure pain in the interspinous area. ⑤ Range of lumbar motion: The degree of limitation of lumbar motion varies greatly depending on factors such as whether it is in the acute stage and the duration of the disease. In mild cases, it can be close to normal, while in the acute phase, lumbar movement can be completely restricted, and even refusal to test lumbar mobility. In general, lumbar flexion, rotation and lateral movement are mainly limited; in cases of combined lumbar spinal stenosis, posterior extension is also affected. (6) Muscle strength and atrophy of the lower limbs: depending on the location of the damaged nerve root, the muscles innervated by the nerve root may show muscle weakness and signs of muscle atrophy. In clinical practice, the circumference of the thigh and calf should be measured and the muscle strength of each group of muscles should be tested routinely, and then compared with the healthy side and recorded, and then compared after treatment. (7) Sensory disturbance: The mechanism is the same as the previous one, depending on the location of the affected spinal nerve roots and the abnormal sensation of the innervated area. The positivity rate is more than 80%, and the posterior type is 95%. In the early stages, the symptoms are mostly skin irritation, followed by numbness, tingling and hyperalgesia. It is not common to see complete loss of sensation because the affected nerve roots are mostly unilateral, so the scope of sensory disturbance is small; however, if the cauda equina is involved (central type and paracentral type), the scope of sensory disturbance is more extensive. (8) Reflex changes: This is also one of the typical signs that are prone to occur in this disease. When the lumbar 4 spinal nerve is involved, knee-jerk reflex disorder may occur, which is active in the early stages and then rapidly becomes hyporeflexic, with the latter being more common in clinical practice. Damage to the lumbar 5 spinal nerve has no effect on the reflexes. The Achilles tendon reflex is impaired when the first sacral nerve is involved. Reflex changes are more significant for the localization of the involved nerve. (2) Special signs: Signs obtained through various special examinations. The main ones with greater clinical significance are: ① Flexion neck test (Lindner’s sign): also known as Lindner’s sign. The patient is asked to stand, lie on his back or sit, and the examiner places his hand on top of his head and bends it forward. The test is positive if there is radiating pain in the affected lower extremity, and negative if the opposite is true. The positive rate for the spinal canal type is over 95%. The mechanism is mainly due to the upward displacement of the dura mater with the flexion of the neck, resulting in the pulling of the spinal nerve roots in contact with the protrusion. This test is simple, convenient, and reliable, and is especially suitable for outpatient and emergency care. ② Straight leg raise test: The patient lies supine and the affected knee is lifted upward in the straightened position, and the angle of passive elevation is measured and compared with the healthy side. This test has been well accepted since it was first proposed by Forst in 1881. The more inferior the nerve root, the greater the positive detection rate (and the smaller the lift angle). In addition, the larger the protrusion, the more extensive the edema and adhesions at the root cuff, the lower the lifting angle. Under normal conditions, the lower extremity can be lifted above 90°, but the angle decreases slightly with age. Therefore, the smaller the lift angle, the greater the clinical significance, but it must be compared with the healthy side; in bilateral cases, 60° is generally the dividing line between normal and abnormal. ③Healthy limb elevation test (also known as Fajcrsztajn sign, Bechterew sign, Radzikowski sign): when the healthy limb is elevated straight leg, the nerve root sleeve on the healthy side can pull the dural sac to distal displacement, thus causing the nerve root on the affected side to move downward as well. When the herniated disc on the affected side is in the axillary part of the nerve root, the nerve root movement to the distal end is restricted, causing pain. If the herniated disc is in the shoulder, the test is negative. When the patient is lying supine during the examination, the presence of sciatica on the affected side is positive when the straight leg on the healthy side is elevated. Laseque’s sign: Some people combine this sign with the former one, while others advocate a separate description. It is positive when the hip and knee are placed in 90° of flexion, and then the knee is straightened to 180°, during which the patient develops posterior radiating pain in the lower limb. The mechanism is mainly due to the stimulation and stretching of the sensitive sciatic nerve during knee extension. (5) Straight leg raise test: Also known as Bragard’s sign, when the straight leg raise test is performed at a positive angle (based on the patient’s complaints of radiating pain), the affected foot is then flexed dorsally to increase the pull on the sciatic nerve. Positive patients complain of increased radiating sciatic nerve pain. The purpose of this test is to exclude the effect of myogenic factors on the straight leg raise test. (6) Supine jerk test: The patient is placed in a supine position and does a jerk of the abdomen and buttocks, so that the buttocks and back leave the bed. At this point, if the patient complains of radiating pain in the sciatic nerve of the affected limb, the test is positive. (7) Femoral nerve pull test: The patient is placed in a prone position with the knee joint of the affected limb fully extended. The examiner elevates the straightened lower limb so that the hip joint is in the hyperextended position, and when the hyperextension reaches a certain level and pain occurs in the femoral nerve distribution area in front of the thigh, it is positive. This test is mainly used to examine patients with herniated discs in lumbar 2 to 3 and lumbar 3 to 4. However, in recent years, it has also been used to detect cases of lumbar 4-5 disc herniation, and its positive rate can be as high as 85% or more. ⑧ Other tests: such as the N nerve or common peroneal nerve compression test, lower limb rotation (internal or external rotation) test, etc., are mainly used for sciatica disorders caused by other causes. The symptoms and signs of lumbar disc herniation with localization significance in common areas are listed in Table 1. Table 2 shows the clinical manifestations of central type lumbar disc herniation. According to the location and direction of the nucleus pulposus protrusion, it can be divided into the following two large sizes. (1) Vertebral body type: That is, the degenerated nucleus pulposus passes through the inferior (common) or superior (rare) fibrous ring, and then passes through the cartilage plate in a vertical or oblique direction into the middle of the vertebral body or the edge of the vertebral body. This type was previously thought to be rare, but in fact, if a thorough examination of patients with low back pain is performed, no less than 10% of patients have this type; autopsy materials indicate that the percentage of this type can be as high as 35%. This type can be subdivided into: ① Anterior margin type: the nucleus pulposus penetrates the edge of the vertebral body (the anterior superior edge of the next vertebral body is the most common), causing a triangular bone block-like appearance at the edge (so clinically misdiagnosed as vertebral body margin fractures occur). This type is clinically more common, and Qu Mianwei (1982) found 32 cases (31.3%) among 102 gymnasts, which is higher than the general incidence of 3%-9%, probably related to the training style and activity of this group of athletes. The mechanism of occurrence is mainly posterior extension of the low back, increased pressure in the intervertebral space, and forward displacement of the nucleus pulposus and protrusion into the vertebral body (Figure 3A). Depending on the course of the disease after prolapse, it may take different forms, and in the later stages, it may form part of the vertebral body edge bones. ②Medium size: the nucleus pulposus passes vertically or nearly vertically upward or downward through the cartilage plate into the vertebral body and forms Schmorl nodule-like changes (Figure 3B). It is not easily diagnosed because it is clinically mild or asymptomatic, and is found in approximately 15% to 38% of autopsies. The protrusions can be large or small; large ones are easily detected by X-rays or CT or MRI, while small ones are often missed. Under normal circumstances, the degenerated nucleus pulposus does not easily pass through the small perforation holes on the cartilage plate, but this type can be caused by acquired damage, thinning of the cartilage plate or coincidental penetration to the remains of vascular channels. (2) Spinal canal type: or posterior type, refers to the nucleus pulposus protruding through the fibrous ring in the direction of the spinal canal. If the nucleus pulposus stops in front of the posterior longitudinal ligament, it is called “disc protrusion”; if it crosses the posterior longitudinal ligament and reaches the spinal canal, it is called “disc prolapse”. According to the anatomical location of the protrusion, it can be divided into the following five types. ①Central type: refers to the protrusion (prolapse) is located in the front of the central part of the spinal canal, mainly causing irritation or compression of the cauda equina. In individual cases, the nucleus pulposus may pass through the dural sac wall into the subarachnoid space. The main clinical manifestations of this type are bilateral lower limbs and bladder and rectal symptoms. Its incidence is about 2% to 4%. ② Central paracentral type: refers to those whose protrusions (prolapse) are located in the center but slightly to the side. Clinically, cauda equina symptoms are the main symptoms, and may be accompanied by radicular irritation symptoms. The incidence is slightly higher than that of the former. (iii) Lateral type: The protrusion is located in the middle of the anterior part of the spinal nerve root and may be slightly deviated. It mainly causes symptoms of radicular irritation or compression; it is the most common clinically, accounting for about 80%. Therefore, when referring to the symptoms, diagnosis and treatment of this disease, most of them are described in this type. The herniation is located on the lateral side of the spinal nerve root and is often in the form of a “prolapse”. Therefore, not only may the nucleus pulposus compress the spinal nerve root at the same node (inferiorly), but the nucleus pulposus may also move up the anterior wall of the spinal canal and compress the superior spinal nerve root. Therefore, if surgical exploration is performed, care should be taken to examine it. It is less common clinically, accounting for about 2% to 5% of cases. (5) The most lateral type: i.e., the prolapsed nucleus pulposus migrates to the anterior side of the spinal canal, or even into the root canal or the lateral wall of the spinal canal. Once adhesions are formed, they are easily missed and may even be overlooked during intraoperative examination, so clinical attention is needed, but fortunately, their incidence is only about 1%.